1 Princess, 1 beefed Minotaur, and a legion of Marlboro class monsters for the Beauty and the Beast fight imo. That way the Beauty, the Beast, and the tentacle fetish are all adequately covered.
For the 5v5v5, are they all undead? That'd be kinda epic, especially at Poeskas Lake North. Only problem is the nasty 9 Sprite cap, but Miluda + Algus + female Time Mages + male Knights on each side or something should do the fight fine.
Chess - 2 male Knight, 2 female Oracle (Bishop), 2 Monk (Rooks [Earth Slash attacks in a line!]), 5 Squire (Pawns). Monks could alternatively be Samurais or Archers though pending on how "Rook" is interpreted, though.
I see a problem with Hi-Ho Boco!, though... the Chocobos will often go before the players and end up out of mount range.
Custer's Last Stand - a bunch of (4-5) male Engineers with various skillsets / equips mounted on various classes of Behemoths (if you didn't do that monster switch thing, sub Red Chocobos). If possible, start the party in two teams in a way so they surround the enemy.
Drakengard! - A ??? Squire (using the blue palette like you see on the lead Squire in the 1.3 Mandalia Plains battle) with Guest Gafgarion's Dark Sword as secondary and Dragon Spirit reaction mounted on a ??? Red Dragon. (Only possible if you do that mountable monster manipulation thing.)
Heretic Hunt - 2 Holy Knights with the Knight sprite, 1 Holy Priest with the Priest sprite, 2 Knight Blades with the Lancer sprite.
Child's Trading Card Thieves! - 5 Thieves. 1 is the male Thief "Zaloog", with a forced pair of (Mythril/Stone?) Guns, Move +2, Speed Gear, Talk Skill secondary. 2 is another male Thief "Gorg", with a forced Scorpion Tail, Two Hands, Basic Skill / Punch Art, high HP / tanking gear, Move-HP UP, MP Switch. 3 is the male Thief "Cliff", with a forced Zorlin Shape + Crystal Shield, Move +2, Move Gear (Speed when Move isn't optimizable with that equip slot), Throw secondary, Defense UP, Hamedo. 4 is the final male thief, "Chick", with a forced Axe, Abandon, Move +3, and Item / Throw Item, possibly a Mantle. 5 is "Meanae", a female Thief with two forced Spears, Izlude's Jump secondary, high Speed setup, Fly, Dragon Spirit.
All I've got for now, as far as decent-or-better ideas go.